Who exactly is the enemy in the continuing U.S. war against terrorism?

In some cases, the answer is: It’s a secret.

When the United States began its war against al-Qaida after the attacks of Sept. 11, 2001, the
identity of the enemy was clear: Osama bin Laden and his followers, and the Taliban who protected
them in Afghanistan. Congress quickly passed a resolution authorizing President George W. Bush to
use “all necessary and appropriate force” against anyone who “planned, authorized, committed or
aided” the 9/11 attacks, plus anyone who harbored them.

That resolution, called the Authorization for the Use of Military Force, remains the legal
underpinning for most counter-terrorist operations today.

Since 2001, however, the target list has grown. Al-Qaida offshoots have sprung up in Yemen,
Somalia, Libya, Mali and, now, Syria. Many of their members had nothing to do with the attacks of
9/11. Most appear more interested in seizing power in their own countries than in striking the
United States.

Nevertheless, both the Bush and Obama administrations decided that the 2001 authorization
covered any group affiliated with al-Qaida that plans operations against the United States or U.S.
interests abroad.

In many cases, that’s a clear standard. When al-Qaida’s Yemen affiliate put a terrorist with
explosives in his underwear on a flight to Detroit, the target was plainly the United States.

But other cases are more ambiguous. Does the Shabab militia in Somalia qualify? They are Islamic
terrorists and a danger to East Africa, but they pose little threat to the United States. Does
Ansar al-Sharia, the group that attacked a U.S. mission in Libya last year but has loose ties to
al-Qaida, fit in? What about al-Nusra Front in Syria, a group born as part of the uprising against
Bashar al-Assad?

All are violent extremists who might gladly kill Americans given the opportunity. But Congress
certainly didn’t have them in mind when it approved the Authorization for the Use of Military
Force.

So Congress is, belatedly, pondering whether the 12-year-old law needs to be revised. For some,
such as Sen. Dick Durbin, D-Ill., the problem is that the resolution has turned into a blank check.
For others, such as Sen. Lindsey Graham, R-S.C., the problem is that the Authorization for the Use
of Military Force doesn’t authorize action against terrorists who aren’t affiliated with al-Qaida.
But both parties agree that Congress ought to take a more explicit role in writing the rules for a
war that appears likely to drag on for another decade or more.

At a stormy hearing of the Senate Armed Services Committee last month, Sen. Carl Levin, D-Mich.,
the panel’s chairman, asked if he could see a list of organizations the administration considers
al-Qaida affiliates.

Pentagon counter-terrorism chief Michael Sheehan sounded unenthusiastic. “A lot of these groups
have very murky membership,” Sheehan said. “They change their name and they lie and obfuscate their
activities. So I think it would be difficult for the Congress to get involved in trying to track
the designation of which are the affiliate forces. We know when we evaluate these forces what they’r
e up to.”

That answer — “trust us,” in effect — didn’t mollify Levin. He asked again for a list.

“I’m not sure there is a list per se,” Sheehan replied. But he promised to put one together.

I asked both the committee and the Pentagon this week whether the list could be publicly
released. Neither gave a clear reply. If there is an enemies list, it is still secret.

If Congress does revise the Authorization for the Use of Military Force, it’s unlikely to make
much of a practical difference in the way the United States fights terrorists. Most members of
Congress still support drone strikes against known terrorists, even U.S. citizens such as Anwar
Awlaki, who was killed by a drone strike in Yemen in 2011. They’d just like to be asked for
permission before the war expands to new countries, such as Mali, where the United States aided
French forces earlier this year.

As President Barack Obama has made clear in Afghanistan and Syria, he’s looking for ways to get
out of old wars, not into new ones. The effect, if any, will mostly be to limit the freedom of
Obama’s successor to use force.

But there is one thing the incumbent president can do: He can tell his Pentagon to be clearer
and less secretive about the criteria it uses to decide which terrorists merit the application of
U.S. military force. If there’s an enemies list, Congress and the public have a right to see it — a
right to know with whom we’re at war.